It is known to use bandaging material impregnated with plaster of Paris for making stiff bandages. These plaster of Paris bandages are too heavy and insufficiently permeable to air and once set they rapidly lose their strength when moist, for example when brought into contact with water. Furthermore, owing to their capacity to absorb and scatter X-rays, they affect the diagnostic results of X-ray photographs and, owing to their inadequate resistance to water, they often give rise to skin irritation brought about by bacterial or mold growth in the bandage.
There have, therefore, been many attempts to provide bandaging materials which are free from these disadvantages. It has for example been attempted to impregnate bandaging material with polymer solutions which harden under exposure to UV light and then to harden the impregnated bandage by irradiation with UV lamp. (Chemical Orthopaedics and Related Research 103, 109-117 (1974)).
The UV lamps required for this purpose are difficult to handle, and moreover, the UV light only reaches the upper layers of the bandage so that the deeper layers harden only after a considerable time if at all. Another serious disadvantage of this method is that while the bandage is being hardened by UV light, the fracture under the bandage cannot be observed by X-rays.
A bandaging material which is capable of stiffening has been described in German Offenlegungsschrift No. 2,353,212. It consists of a flexible basic material treated with substances which contain oxycarbonyl isocyanate groups. The bandaging material described in German Offenlegungsschrift No. 2,353,212 was not successful in practice, partly because practically insurmountable difficulties were encountered in the manufacture of the bandaging material owing to the extremely high reactivity of oxycarbonyl isocyanates and partly because casts or supporting bandages made from these materials were not strong enough for the purposes required. Furthermore, the high reactivity of oxycarbonyl isocyanates rendered the impregnated bandaging material extremely unstable in storage since the prepolymers with oxycarbonyl isocyanate and urethane groups used according to German Offenlegungsschrift No. 2,353,212 rapidly harden even in the absence of atmospheric moisture.
The process described in German Offenlegungsschrift No. 2,357,931 for producing hardened bandages is also generally unsuitable for medical or surgical purposes because the process of hardening by the action of atmospheric moisture described in that Offenlegungsschrift takes too long.
The present invention provides a novel process for producing supporting bandages for surgical and veterinary surgical use which is substantially free from the disadvantages of the above mentioned processes known in the art. The process according to the invention described below is distinguished in particular by the following advantages:
1. The material is highly permeable to X-rays so that X-ray photographs can be taken through the bandage without any shadow PA1 2. the bandages required for producing a given supporting effect are much lighter than the known plaster of Paris bandages providing the same effect, the saving in weight being up to about 80%; PA1 3. the bandages are resistant to water; PA1 4. the bandages attain weight bearing strength after only about 10 to 15 minutes; PA1 5. the heat of reaction produced during hardening of the bandage is slight compared with that of conventional plaster of Paris bandages; PA1 6. both application of the bandages and their removal after completion of the healing process are extremely simple and clean; PA1 7. the risk of skin irritation due to bacteria or molds is much smaller than in known plaster of Paris bandages; PA1 8. no apparatus is required for applying the bandage; PA1 9. the bandages according to the invention have excellent permeability to air and hence breathing activity. PA1 (1) Woven, knitted or warp knitted textile fabrics having a weight of about 20 to 200 g/m.sup.2, preferably about 40 to 100 g/m.sup.2 and a thread count of preferably about 2 to 20 threads per centimeter in the longitudinal and transverse direction. The woven or knitted textile fabric may be produced from any natural or synthetic yarn, but it is preferred to use fabrics made of mixed yarns containing both hydrophobic filaments or fibers with a high elastic modulus (for example polyester) and hydrophilic natural or synthetic filaments or fibers (for example cotton or polyamide). PA1 (2) Woven, knitted or warp knitted glass fiber fabrics weighing from about 60 to 500 g/m.sup.2, preferably about 100 to 400 g/m.sup.2 and having a thread count of preferably about 2 to 20 per centimeter in the longitudinal and transverse direction. Glass fiber fabrics which have been treated with a hydrophilic sizing agent are preferred. PA1 (3) Bonded or non-bonded or stitched non wovens based on inorganic and preferably organic fibers and having a weight of about 30 to 400 g/m.sup.2 preferably about 50 to 200 g/m.sup.2. PA1 (1) Low molecular weight polyols having a molecular weight of from about 105 to 300 which contain tertiary nitrogen atoms and are free from ether groups, e.g. N-methyl-diethanolamine, N-ethyldiethanolamine, N-methyl-dipropanolamine, triethanolamine or tripropanolamine; PA1 (2) polyester polyols having a molecular weight of from about 300 to 2000, preferably about 800 to 1500, containing tertiary nitrogen atoms, which polyester polyols can be obtained by the reaction of polybasic acids with amino alcohols of the kind mentioned in (1) above as examples, if desired together with polyhydric alcohols which are free from nitrogen. Suitable polybasic acids include, for example, adipic acid, phthalic acid and hexahydrophthalic acid. Suitable nitrogen free polyhydric alcohols for the preparation of the polyesters include, for example, ethylene glycol, tetramethylene glycol, hexamethylene glycol and trimethylolpropane. PA1 (3) Polyether polyols with tertiary amino nitrogen atoms having a molecular weight of from about 300 to 2000, preferably about 800 to 1500, which can be obtained in known manner by the alkoxylation of nitrogen containing starting compounds. Suitable starting compounds of this kind include, for example, ammonia, the amino alcohols mentioned in (1) above as examples and amines containing at least two-NH-bonds, e.g. ethylene diamine, aniline and hexamethylenediamine. Suitable alkylene oxides for the preparation of the polyethers include, for example, ethylene oxide and propylene oxide. Propoxylation products of the above mentioned nitrogen containing starting materials are particularly preferred.